Triangular-shaped writing instrument with abrasive surface on upper portion



FIG. 1 is a top plan view of a triangular-shaped writing instrument with abrasive surface on upper portion showing our new design;

FIG. 2 is a side elevation view thereof;

FIG. 3 is a bottom plan view thereof; and,

FIG. 4 is a perspective isometric view thereof. 

The ornamental design for a triangular-shaped writing instrument with abrasive surface on upper portion, as shown and described. 